Apparatus for the production of zinc by the reduction of zinc oxides in multiple-retort furnace



Dec. 17, 1963 N, HOFFAl-r 3,114,787

APPARATUS FON THE: PRODUCTION OF ZINC BY THE REDUCTION OF ZINC OxIDEs IN MULTIPLE-RETORT FURNACE Dec. 17, 1963 N. HoFFAlT 3,114,787

APPARATUS PoR TRE PRODUCTION oF zTNc BY THE REDUCTION OF ZINC OXIDES IN MULTIPLE-RETORT FURNACE Filed Feb. 14, 1961 4 Sheets-Sheet 2 Dec. 17, 1963 N. HoFFAlT 3,114,787

APPARATUs FUR TRE PRODUCTION oF ZINC BY THE REDUCTION 0F ZINC oxIDEs IN MULTIPLE-RETCRT FURNACE Filed Feb. 14, 1961 4 Sheets-Sheet 3 N. Hol-FAIT 3,114,787 APPARATUS FOR THE PRODUCTION OF' ZINC BY THE REDUCTION Dec. 17, 1963 OF' ZINC OXIDES IN MULTIPLE-RETORT FURNACE 4 Sheets-Sheet 4 Filed Feb. 14, 1961 United States Patent O i 3,114,787 APPARATUS Fon Tim rnoDUCrioN oF ziNC er THE REDUCTEN F ZINC XIDES IN MULTI- PLE-RETORT FURNACE Nicolas` Hoiait, Foret-Trooz, Belgium, assigner to Societe Anonyme Metailurgique de Prayon, Foret-Trooz,

The invention relates to the production of Zinc by the reduction of zinc oxides, notably of zinc oxide minerals, in a multiple horizontal retort furnace. Furnaces of this type generally comprise several hundreds of retoits opening into the two opposed faces of the furnace, these retorts being individually charged.

In known installations, the zinc vapours produced by the retorts are condensed in individual or collective condensers that always function in a discontinuous manner. Those condensers find themselves idle during the cleaning out and charging periods for the retorts, while they are fed by gas of variable yield and composition during the reducing cycle.

Because the gaseous yield is high during the early hours of the reduction, the condensers must be dimensioned appropriately large. In consequence, during the last hours of the reduction, when the gaseous yield is less, the condensers are actually too big. It follows therefore that the eiliciency of the condensers can only be maintained through the reduction cycle by controlling by the use of appropriate devices their thermal operation in accordance with the variations in the yield.

As regards a zinc furnace, its heat requirement is governed by' the performance of the condensers and their ability for adjustment to different gaseous yields. Because of this, it is necessary to follow, during each cycle, a diagram showing the reduction and, therefore, the heat requirement.

It is an object of the present invention to overcome these disadvantages and to provide a construction of zinc furnace with horizontal retorts that enables one or several collective condensers to be fed with gas of substantially constant yield and composition. In consequence, the collective condenser or condensers can be constructed to operate in a constant and most favourable thermal manner. Moreover, since the variations in yield during the reduction cycles of the retorts do not affect the condensation, the heat supply to the furnace can be maintained steady and at constant temperature.

With that object, the invention envisages a process that consists essentially in subdividing the whole of the retorts into a number of cells each comprising at least two retorts, separately and continuously collecting the gaseous mixture, mainly composed of Zinc vapours and CO, produced in the retorts of each of the cells, continuously gathering into a single stream the gaseous mixture produced in a number of the cells, maintaining the said gaseous mixture at a temperature greater than the condensation temperature of zinc, preferably at least about 900 C., conducting the said stream to apparatus for recovery of its zinc content, independent of or connected to the furnace itself, and isolating each of the said cells from the common stream during the time required for cleaning out and recharging the retort or retorts comprised in it. These last operations can thus be staggered in time between the severalV cells, while the furnace is heated continuously to a practically constant temperature, so as to provide a continuous process leading to a substantially constant yield of 'zinc vapours from the whole of the cells. The said operations can thus be effected by a labour force spread over 24 hours and the effective time of reduction can,

3,114,787 Patented Dec. 17, 1963 if need be, be adjusted according to the requirements of each of the cells. At any rate, the idle time for each cell is restricted to what is required for cleaning out and recharging its small number of retorts. It is thus reduced to a minimum, which represents a corresponding reduction of the total time of the Working cycle. The Zinc vapours can, in any desired quantity, be transformed at will into metallic zinc or into zinc powders. The furnace can be held to the same practically constant working temperature, thus avoiding the necessity for periodically changing the heating rate and eliminating the resultant loss of heat.

The invention likewise envisages a furnace for the production of Zinc by the reduction of zinc oxides, of the type comprising a plurality of retorts disposed in superimposed rows at the faces of the furnace, and is characterized essentially by the fact that the retorts open directly into the Vfaces and are divided into numerous cells each comprising at least two retorts, the retorts of each cell discharging into a sealed primary collector disposed outside the face of the furnace and having a movable wall to provide access to the retorts, while several of the primary collectors are each connected, by a conduit that can be shut oil', to a main collector adapted to beconnected to an apparatus, independent of or connected to the furnace itself, for recovering the Zinc from the gaseous mixture yielded by the retorts, the whole of the primary and main collectors and the said conduits being `conditioned in such a manner as to maintain the said gaseous mixture at a temperature higher than the condensation temperature of zinc, preferably at least about 900 C., while the furnace is adapted to be equipped with continuous heating means.

According to an advantageous embodiment of the invention, the said primary and main collectors and the said conduits that connect them together are disposed in intimate Contact with the hot masonry of the furnace, the whole being insulated in a manner to maintain the desired temperature automatically."

The furnace according to the invention may equally be made by conversion of an existing furnace, of the type in which recesses containing a reduced number of retorts are provided in the face of the furnace. According to the invention, each recess is then used as a primary collector, and, for this purpose, it is closed by a movable door of heat-insulatingmaterial, preferably arched externally, and luted tightly between the walls of the recess, so as to reduce the section to that'desired for the primary collector, while the connecting conduit to the main collectors is tted into the roof of the recess. If the lower parts of the arch of the furnace are exposed, as is often the case with furnaces of the type in question, the main collectors are advantageously disposed in relation to the arch to rest directly on its lower parts, to lead the said gaseous mixture to the ends of the furnace.

Other features and advantages of the invention will appear from a description of "an embodiment. of the invention, notably as applied to an existing furnace, given below with reference to the accompanying diagrammatic drawings, in which:

FIGURE l is a fragmentary plan view of ythe furnace;

FIGURE Z is a vertical section on the line I-I-II of FGURE `1;

FGURE 3 is a View to URE 2;

FIGURE 4 is `a perspective view of a part of the furnace face;

` FIGURE 5 is a View, similar to FIGURE 3, of a modiijed construction of the corresponding part of .the furnace, and FIGURE 6r is a horizontal section approximately on the broken line VI-Vl of FIGURE 5.

a larger scale of part of FIG- In the drawings, 1 shows the arch of the furnace and 2 its faces. The retorts 3` are luted tightly in superimposed rows in the faces, the number of retorts generally :amounting to several hundreds. Recesses 4 are formed in the faces, each recess embracing two vertical rows of retorts, amounting to eight retorts in the example shown, this number obviously being capable of variation according to the type of furnace. In an existing furnace of this type, the retorts open directly into condensers disposed at the furnace face, for example individual condensers.

Having regard to the rational realisation of the invention, the furnace must be equipped with a heating system capable of operating continuously, for example a continuous gas producer, by-products of petroleum distillation, or natural gas.

In the example shown, the eight retorts open into one single recess forming a cell.

The recesses are closed by movable doors 5, so as to convert them into primary collectors 6, into which the retorts open freely, the retorts not being provided with any condensing device. The doors are made of material sutiiciently heat insulating to maintain a temperature such that the zinc vapours `do not condense in the primary collectors. They preferably have a metal frame to make them at the same time light and robust. The doors 5 are luted tightly between the walls of the recesses 4 and are with advantage arched externally to reduce the section of the collector.

The gaseous mixture is lwithdrawn fro-m each primary collector 6 by a conduit 7 opening into the roof of the recess 4 and connected to a main collector, with `a damper interposed -to enable the said conduit lto be shut off. In the example shown in FIGURES t1-4, the vertical conduit 7 is extended by la horizontal conduit 8 presenting a seating 9 (FIGURE 3) to a valve member 10 that can be actuated from outside by -means of a control rod 11 slidable in sealed manner through the refractory masonry surrounding the conduits 7, v8. The con-duit 8 opens into a main collector 12 that is disposed directly on the lower part of the arch 1, which lower part is exposed in the type of furnace in question. The collector 12 thus benelits materially from the hea-t of the arch. Moreover, the collectors 12 and the conduits 7, 8 carrying the gaseous mixture formed in the retorts are clad in insulating bricks, both above and towards the face of the furnace. The whole of the above described arrangements ensures that the said gaseous mixture is held at the highest possible temperature. The furnace operating at a tempenature of about 1300 C. in the working zone of the furnace, i.e., in the zone containing the retorts 3, the described arrangements enable the said gaseous mixture to be easily held lat a temperature reaching to :at least about 900 C., right to the outlets of the main collectors 12 located at the ends of the furnace. Y

The parts having direct contact with the Zinc vapours, notably the conduits 7, `8, the dampers 9, 10; and the collectors 12, are preferably of silicon carbide, which has a strong resistance to these vapours.

In the construction shown in FIGURES 5 and 6, the conduit 7 opens into the bottom of a chamber A14, closed by a slab 15 and having a side Wall 16 inclined to the vertical and ltowards the outside, in this case formed by a wall of a main collector 12. An opening 17 in this wall establishes a connection between the chamber '14 and the collector 12. A valve member 18 normally iits )against the wall 16 and closes the opening 17. It then also shuts oif the mouth 0f the conduit 7 and for this purpose the valve member 18 preferably has on its lower face an annular rib 19 to enter a recess 20* surrounding the mouth yof the conduitV 7 and iilled with sand or the like to form a sealed joint. A rigid -rod 21 for the valve member 18 passes through the slab 1'5 for operation of the valve from the outside.

To allow for periodical cleaning, a plug 22 is fitted into an opening in the wall lof the collector 12 and can be lifted into a cavity 23, closed by a slab 24, by means of a rod 25 accessible from the outside. A channel 26 opens into the cavity 23 and also to the outside. The arrangement is such that, when the valve 18- :and the plug 22 are lifted, a rod inserted through the channel 26 can pass thr-ough the opening for the plug 22 and through the 'opening 17 to reach the mouth of the conduit 7, and this allows the various parts to be very quickly cleaned when required.

In the example shown, the line A -A in FIGURE 1 indicating the middle of the furnace, presumed to be of great length, there have been provided four main collectors 12. Obviously their number could be altered, for example reduced to two.

At the outlets of the main collectors, the gaseous mixture can be led to any device 13 whatsoever for the recovery of their Zinc content, whether by condensation into ordinary zinc, or by the manufacture of rened zinc, or by the manufacture of zinc powders, according to any appropriate process. The form in which the zinc is finally recovered can thus be selected as desired. If so desired, this form can be diierent for the discharge of the different main collectors.

The invention enables a continuous process for the production of zinc to be achieved, in contrast to what is the case with known multiple-retort furnaces. The charging of the retorts of the 'different recesses can actually be staggered in time so as to ensure a substantially constant d-ischarge of zinc vapours at the outlet point of the main collectors i12. The charging cycle can be adjusted from one recess to another, to enable a recess to be discharged when the charge in its retorts has been correctly reduced, neither too soon (thus avoiding loss in the residues, and the substantial elimination of the need to return them for fresh distillation, as Iis a quite important matter with the usual processes), nor too late (which would represent a loss of heat expended uselessly)i What I claim is:

1. A furnace for the production of zinc by the reduction of material containing zinc oxides, said furnace comprising a face defining a side of said furnace, a plurality of cells arranged along said face, each cell cornprising at least two retorts disposed generally horizontally inside said face, each cell including a primary collector disposed outside the face of said furnace and a movable wall sealing said cell, each primary collector having one side formed by a portion of said face of said furnace, said retorts of each said cell opening freely into the associated primary collector, an individual connecting conduit associated with each said primary collector and a main collector disposed in receiving relationship with the conduits of a plurality of said primary collectors, each said conduit having a closure means including a valve controllable from outside said furnace for shutting off said conduit, apparatus disposed in receiving relationship to said main collector for recovering zinc from the gaseous mixture collected and discharged by said main collector, and means for maintaining said primary, said main Collectors and said conduits at a temperature higher than the condensation temperature of zinc.

2. A furnace for the production of zinc by the reduction or material containing zinc oxides, said furnace comprising a face defining a side of said furnace, a plurality of cells arranged along said face, each cell comprising at least two retorts disposed generally horizontally inside said face, each cell including a primary collector disposed outside the face of said furnace and a movable wall sealing said cell, each primary collector having one side formed by a portion of said face of said furnace, said retorts of each said cell opening freely into the associated primary collector, an individual connecting conduit associated with each said primary collector and a main collector disposed in receiving relationship with the conduits of a plurality of said primary collectors, each said conduit having a closure means including a valve controllable from outside said furnace for shutting oi said conduit,

and apparatus disposed in receiving relationship to said main collector for recovering zinc from the gaseous mixture collected and discharged by said main collector, said primary and main collectors and said conduits being disposed in intimate contact with hot portions of said furnace.

3. A furnace for the production of zinc by the reduction of material containing zinc oxides, said furnace comprising a face defining a side of said furnace, a plurality of cells arranged along said face, each cell comprising at least two retorts disposed generally horizontally inside said face, each cell including a primary collector defined by a recess in the outside of the face of said furnace and a movable wall sealing said cell, each primary collector having one side formedby a portion of said face of said furnace, said retorts of each said cell opening freely into the associated primary collector, an individual connecting conduit associated with each said primary collector and fitted in the face of said furnace above said recess and a main collector disposed in receiving relationship with the conduits of a plurality of said primary collectors, each said conduit having a closure means including a valve controllable from outside said furnace for shutting olf said conduit, and apparatus disposed in receiving relationship to said main collector for recovering zinc from the gaseous mixture collected and discharged by said main collector, said primary and main collectors and said conduits being disposed in intimate contact with hot portions of said furnace, said movable wall being of heat insulating material towards the outside and defining a door luted tightly between the walls of said recess.

4. A furnace for the production of zinc by the reduction of material containing zinc oxides, said furnace comprising a face defining a side of said furnace, a plurality of cells arranged along said face, each cell comprising at least two retorts disposed generally horizontally inside said face, each cell including a primary collector disposed outside the face of said furnace and a movable wall sealing said cell, said retorts of each said cell opening freely into the associated primary collector, an individual connecting conduit associated with each said primary co1- lector and a main collector disposed in receiving relationship with the conduits of a plurality of said primary collectors, each said conduit having a closure means including a valve controllable from outside said furnace for shutting off said conduit, and apparatus disposed longitudinally in receiving relationship to said main collector for recovering zinc from the gaseous mixture collected and discharged by said main collector, said primary and main collectors and said conduits being disposed in intimate contact with hot portions of said furnace and said main collector being disposed on the roof of said furnace.

5. A furnace for the production of zinc by the reduction of material containing zinc oxides, said furnace comprising a face defining a side of said furnace, a plurality of cells arranged along said face, each cell comprising at least two retorts disposed generally horizontally inside said face, each cell including a primary collector disposed outside the face of said furnace and a movable wall sealing said cell, said retorts of each said cell opening freely into the associated primary collector, an individual connecting conduit associated with each said primary collector and a main collector disposed in receiving relationship with the conduits of a plurality of said primary collectors, each said conduit having a closure means including a valve controllable from outside said furnace for shutting off said conduit, and apparatus disposed in receiving relationship to said main collector for recovering zinc from the gaseous mixture collected and discharged by said main collector, said primary and main collectors and said conduits being disposed in intimate contact with hot portions of said furnace, said closure means comprising a movable valve member and a solid stationary seat in the associated conduit and a slidable rod extending through and sealed relative to the wall of said furnace.

6. A furnace for the production of zinc by the reduction of material containing zinc oxides, said furnace comprising a face defining a side of said furnace,` a plurality of cells arranged along said face, each cell comprising at least two retorts disposed generally horizontally inside said face, each cell including a primary collector disposed outside the face of said furnace and a movable wall sealing said cell, said retorts of each said cell opening freely into the associated primary collector, an individual connecting conduit associated with each said primary collector and a main collector disposed in receiving relation- `ship with the conduits of a plurality of said primary collectors, apparatus disposed in receiving relationship to `said main collector for recovering zinc from the gaseous mixture collected and discharged by said main collector, means for maintaining said primary, said main collectors and said conduits at a temperature higher than the condensation temperature of zinc, a chamber being disposed intermediate each said primary collector and said main collector, said chamber having a bottom opening in communication with said primary collector and an inclined side wall, an aperture opening into said main collector, and a valve having an inclined side wall adapted to closely lit said inclined side wall of said chamber and shut said aperture and a bottom portion for closing said bottom 4opening and said valve having a rod extending upwardly and outwardly of said chamber and being vertically movable in said chamber.

7. A furnace for the production of zinc by the reduction of material containing zinc oxides, said furnace comprising a face defining a side of said furnace, a plurality of cells arranged along said face, each cell comprising at least two retorts disposed generally horizontally inside said face, each cell including a primary collector disposed outside the face of said furnace and a movable wall sealing said cell, said retorts of each said cell opening freely into the associated primary collector, an individual connecting conduit associated with each said primary collector and a main collector disposed in receiving relationship with the conduits of a plurality of said primary collectors', apparatus disposed in receiving relationship to said main collector for recovering zinc from the gaseous mixture collected and discharged by said main collector, means for maintaining said primary, said main collectors and said conduits at a temperature higher than the condensation temperature of zinc, a chamber being disposed intermediate each said primary collector and said main collector, said chamber having a bottom opening in communication with said primary collector and an inclined side wall, an aperture opening into said main collector, and a valve having an inclined side wall adapted to closely fit said inclined side wall of said chamber and shut said aperture and a bottom portion for closing said bottom opening and said valve having a rod extending upwardly and outwardly of said chamber and being vertically movable in said chamber, said chamber having a recess extending around said bottom opening and filled with sand and said valve bottom being provided with an annular projection received in said recess to close said bottom opening.

8. A furnace for the production of zinc by the reduction of material containing zinc oxides, said furnace comprising a face dening a side of said furnace, a plurality of cells arranged along said face, each cell comprising at least two retorts disposed generally horizontally inside said face, each cell including a primary collector disposed outside the face of said furnace and a movable wall sealing said cell, said retorts of each said cell opening freely into the associated primary collector, an individual connecting conduit associated with each said primary collector and a main collector disposed in receiving relationship with the conduits of a plurality of said primary collectors, apparatus disposed in receiving relationship to said main collector for recovering zinc from the gaseous mixture collected and discharged by said main collector,

means for maintaining said primary, said main collectors and said conduits at a temperature higher than the condensation temperature of zinc, a chamber being disposed intermediate each said primary collector and said main collector, said chamber having a bottom opening in communication with said primary collector and an inclined side Wall, an aperture opening into said main collector, and a valve having an inclined side Wall adapted to closely fit said inclined side Wall of said chamber and shut said aperture and a bottom portion for closing said bottom opening and said valve having a rod extending upwardly and outwardly of said chamber and being vertically movable in said chamber, said chamber having a recess eX- tending around said bottom opening and filled with sand and said valve bottom being provided Ywith an annular projection received in said recess to close said bottom References Cited in the le of this patent UNITED STATES PATENTS 1,994,347 Ginder Mar. 12, 1935 2,413,374 Phillips et al Dec. 31, 1946 2,493,823 Morrison June 10, 1950 2,886,303 Rusiano May 12, 1959 

1. A FURNACE FOR THE PRODUCTION OF ZINC BY THE REDUCTION OF MATERIAL CONTAINING ZINC OXIDES, SAID FURNACE COMPRISING A FACE DEFINING A SIDE OF SAID FURNACE, A PLURALITY OF CELLS ARRANGED ALONG SAID FACE, EACH CELL COMPRISING AT LEAST TWO REPORTS DISPOSED GENERALLY HORIZONTALLY INSIDE SAID FACE, EACH CELL INCLUDING A PRIMARY COLLECTOR DISPOSED OUTSIDE THE FACE OF SAID FURNACE AND A MOVABLE WALL SEALING SAID CELL, EACH PRIMARY COLLECTOR HAVING ONE SIDE FORMED BY A PORTION OF SAID FACE OF SAID FURNACE, SAID RETORTS OF EACH SAID CELL OPENING FREELY INTO THE ASSOCIATED PRIMARY COLLECTOR, AN INDIVIDUAL CONNECTING CONDUIT ASSOCIATED WITH EACH SAID PRIMARY COLLECTOR AND A MAIN COLLECTOR DISPOSED IN RECEIVING RELATIONSHIP WITH THE CONDUITS OF A PLURALITY OF SAID PRIMARY COLLECTORS, EACH SAID CONDUIT HAVING A CLOSURE MEANS INCLUDING A VAALVE-CONTROLLABLE FROM OUTSIDE SAID FURNACE FOR SHUTTING OFF SAID CONDUIT, APPARATUS DISPOSED IN RECEIVING RELATIONSHIP TO SAID MAIN COLLECTOR FOR RECOVERING ZINC FROM THE GASEOUS MIXTURE COLLECTED AND DISCHARGED BY SAID MAIN COLLECTOR, AND MEANS FOR MAINTAINING SAID PRIMARY, SAID MAIN COLLECTORS AND SAID CONDUITS AT A TEMPERATURE HIGHER THAN THE CONDENSATION TEMPERATURE OF ZINC. 